Pat Barber wrote:
Phisherman wrote:

A better method is to use a 3/8" thick ply clamped to the fence, make
a cut, remove the ply, make the second cut. This is more accurate and
repeatable.

That assumes a perfect piece of plywood that is "exactly"
3/8" which is extremely rare.

I usually have some left over Starboard
http://www.kingstarboard.com/CMS/Med...20Brochure.pdf
, which is a staple building product in the marine industry, laying
around. I use strips of it for all sorts of things, including fence
shims. I rip it to the right size, then scrape or plane until smooth.
It's stable, nothing sticks to it, and it's slick as snot so the boards
slide much easier.

R